Turnbull K J, Brown B L, Dobson P R
Division of Oncology and Cellular Pathology, University of Sheffield Medical School, UK.
Leukemia. 1999 Jul;13(7):1056-61. doi: 10.1038/sj.leu.2401438.
In the present study we have shown that the cancer therapeutic drug, daunorubicin, induces apoptosis in the human lymphoblastic leukemia cell line Jurkat E6.1. This effect was both dose-and time-dependent with nuclear fragmentation detectable by 8 h. Caspases have been implicated in pro-apoptotic events. By utilizing synthetic fluorochrome-linked substrates of the caspases, we observed that a caspase-3-like enzyme had dramatically increased activity (3340 130% with respect to basal levels) in response to daunorubicin treatment. Furthermore, by using an inhibitor to caspase-3, Ac-DEVD-CHO, we have shown that activation of a caspase-3-like enzyme appears to be necessary for nuclear fragmentation and apoptotic body formation, but is not required for chromatin condensation. In contrast, a general caspase inhibitor, Z-VAD-fmk, inhibited all apoptotic parameters measured. Ceramide has been implicated in daunorubicin-induced apoptosis in human myeloid leukemia cells. However, in Jurkat cells, caspase activation does not appear to be a consequence of ceramide generation since, although ceramide levels were elevated through the action of ceramide synthase in response to daunorubicin treatment, this occurred with slower kinetics than either nuclear fragmentation or caspase activation. In contrast, caspase inhibitors abrogated ceramide elevation induced by DNR treatment, suggesting that ceramide synthase may be a downstream target for caspase action. Therefore, daunorubicin-induced apoptosis does not appear to be mediated by ceramide in the lymphoblastic leukemia cell line, Jurkat E6.1. Instead, caspase 3 activity appears to be necessary, but not sufficient for this process.
在本研究中，我们已表明癌症治疗药物柔红霉素可诱导人淋巴细胞白血病细胞系Jurkat E6.1发生凋亡。这种效应呈剂量和时间依赖性，8小时时可检测到核碎裂。半胱天冬酶与促凋亡事件有关。通过使用半胱天冬酶的合成荧光染料连接底物，我们观察到一种类半胱天冬酶-3的酶在柔红霉素处理后活性显著增加（相对于基础水平增加了3340±130%）。此外，通过使用半胱天冬酶-3抑制剂Ac-DEVD-CHO，我们已表明类半胱天冬酶-3的酶的激活似乎是核碎裂和凋亡小体形成所必需的，但不是染色质凝聚所必需的。相比之下，一种通用的半胱天冬酶抑制剂Z-VAD-fmk抑制了所有测量的凋亡参数。神经酰胺与柔红霉素诱导人髓性白血病细胞凋亡有关。然而，在Jurkat细胞中，半胱天冬酶激活似乎不是神经酰胺生成的结果，因为尽管通过神经酰胺合酶的作用，柔红霉素处理后神经酰胺水平升高，但这一过程的动力学比核碎裂或半胱天冬酶激活更慢。相比之下，半胱天冬酶抑制剂消除了DNR处理诱导的神经酰胺升高，表明神经酰胺合酶可能是半胱天冬酶作用的下游靶点。因此，在淋巴细胞白血病细胞系Jurkat E6.1中，柔红霉素诱导的凋亡似乎不是由神经酰胺介导的。相反，半胱天冬酶3活性似乎是这一过程所必需的，但并不充分。
